Hygrometer operated switch



Feb. 13, 194@ K, F SCHOEW HYGROMETER OPERATED SWITCH Filed Aug. 24, 1935 Jarl Johoew,

Patented Feb. 13, 1940 UNITED STATES PATENT OFFICE Application August 24,

2 Claims.

This invention relates to improvements in electrical switches, and its objects are as follows:

First, to provide an electrical switch with an associated hygrometer for operating said switch according to varying moisture conditions yin the surrounding atmosphere, especially in the atmosphere of mines wherein the switch is adapted to be used for the purpose of actuating certain signal apparatus.

Second, to make an effective air seal between the air chamber and electrical'switch compartment for the chief purpose of excluding explosive gases from said compartment and thereby preventing their ignition by any sparking that might occur therein.

Third, to utilize the partition which separates the air chamber from the electrical switch compartment as the mount for the means which ymakes the foregoing air seal around the turnable pointer shaft which shaft extends from the chamber into the compartment.

In the drawing:

Figure l is a sectional view of the improved switch, parts being shown in elevation, and the electrical wiring being indicated diagrammatically.

Figure 2 is a cross section taken on the line 2-2 of Fig. 1.

Figure 3 is a detail section of the structure which makes the air .seal around the pointer shaft.

Figure 4 is a vertical section taken on the line 4-4 in Fig. 2.

Figure 5 is a vertical section taken on the line 5-5 of Fig. 3.

Figure 6 is a detail view of the swingable switch arm, illustrating the use of a spring for returning said arm in lieu of the weight for that purpose illustrated in Fig. 1.

This application is a continuation in part of an application for patent for hydrometer operated switch flied by Karl F. Schoew, August 31,

1932, Serial No. 631,261 issued November 5, 1935,

as patent Number 2,019,635. The instant construction is identical in principle with the chief structure on which the foregoing application is based, but embodies some changes which it has been found are an additional advantage.

The switch, generally designated 4, comprises a casing of cylindrical shape (but not necessarily so), which casing is composed of cylindrical members 6, 1. The member 6 is internally threaded part way as at 8 to admit a closure 9 which is screwed in place to form a back. Flanges I0 and II on adjacent ends of the members 6, 1 are suitably secured in common to a partition I3 which divides the casing into an air chamber I4 and an electrical switch compartment I5.

A screened window I6 provides access of the outer air to the interior of the chamber I4. The

1935, Serial No. 37,763

compartment I5 is made as air tight as possible, chiefly for the purpose of excluding explosive gases from the electrical switch parts which it contains. It is regarded desirable to state that in mines containing a gaseous atmosphere electrical apparatus is permitted only when the electrical parts are sealed from the air. The sealing means herein provided is, therefore, a provision for safety in that it prevents the ignition of an explosive gaseous mixture.

Rubber washers I8 are used on each side of a cover glass I9 at the front of the switch, said washers engaging opposite sides of the glass near the rim and being pressed against the enlarged end 20 of the cylindrical member 1 when the bezel 2| is screwed home. Situated in the air chamber |4 is a hygroscopic metallic absorption element 95. This is made in spiral form (Fig. fl) and it is capable of lengthening and contracting by the atmospheric moisture conditions to which it lis subjected. One end of it is anchored to the partition I3. The other end of it is secured at 96 to the pointer shaft 25.

A bracket 91 (Fig. 2) constitutes the foregoing anchorage for the rst end of the absorption element; this together with a screw 98 which secures the bracket in place on the partition. The bracket, screw and pointer shaft are electrically separated from the partition I3 by insulation 99. The bracket has holes |00 in which the arms of a clamp yoke |0I have limited sliding movement when a set screw |02 is tightened or loosened. The bent ends |03 (bent to position after inserting the armsof the yoke) bear down upon the absorption element nearits free end and hold the element to whatever adjustment the screw |02 may have been set for. The adjustment is made, taking in more or less of the loose end of the element (Fig. 4), until aproper reading on the humidity scale is obtained, whereupon the set screw |02 is tightened.

A plurality of contacts is under control of the pointer 31, one of these being a freely swingable brass (or similar metal) arm |04 the other a pin |05. This pin and a similar one |06 limit the swinging of the arm |04. Swinging in one direction is accomplished by a stud |01. This stud is carried by an arm |08 which is indirectly ailixed to the shaft 25 as is the pointer 31. The stud |01 |04. The arm |04 is freelyswung from a support |09 fixed on the partition I3 (Fig. 2), the arm being held in engagement with the pin |05 (unless disengaged by the stud |01), by a Weight H0 which is afiixed to said arm in any convenient way.

While the foregoing weight constitutes the preferred means for normally holding the arm |04 in engagement with the pin 05, it is contemplated that a spring 22 (Fig. G) shall-,be used in substitution. Ihe opposite ends of this spring are attached t0 an ear 23 on the arm |04 and apin 24 on the support |09. The spring Vis partly wrapped around the support as shown, and its position between the ear and pin ciers the additional advantage of holding the hub of the arm in place on the support.

Indicia 13 comprises the words dangerous and safe. Safe means a relative humidity of 80% or over, while Dangerous applies to any condition less than 80% relative humidity. This indicia is now printed or otherwise applied to an arcuate target l i3 which is supported on the partition E3 by spacers H4 (Fig. 2).

Signal means are used in conjunction with the switch, these being shown as consisting of white and red lamps 03 and 055. A suitable source of current is designated H5. one side of each of the lamps to one side of the current source. The other side of the latter is connected by means of a wire to the support |09 of the arm |04, one of three binding posts 02 being connected in the wire. The other side of the lamp 63 is connected by a wire H0 with the screw 98 (Fig. 2) from which current is conductable to the pointer shaft 25. The other side of the lamp is connected by a wire `H9 to the pin |05.

The following means provides an effectual seal between the air chamber I4 and switch compartment i5; a plate bushing |24 is secured to one side of the partition I3 by screws or equivalent means |25. These screws traverse an extensionof one ofthe insulating elements 99 and go through insulating plugs |26 in the plate bushing for the purpose of preventing a short circuit between the shaft 25 andA the partition |3. The

bushing |24 has a threaded nipple |27 which isY screwed into a bushing |20 onthat side of the partition I3 opposite to the plate bushing.. |24.y The two bushings are intertted and they have bores in which the shaft 25 is turnably mounted,

#to the sleeve in the region of the slit, and when the clamping means is tightened the sleeve is effectually compressed upon the shaft so as to` The adjacent parts of the tween the bushing |20 and the adjacent side of the partition |3. These gaskets are moistened with oil which improves their sealing qualities. The operation `is readily understood.v 'Ihe A wire |10 connects as previously l pointer shaft 25 is adapted to turn either clockwise or counter-clockwise, these turnings being the direct result of alengthening of the element 25 (Fig. 4) as by the accretion of moisture, or a shortening thereof by the loss of moisture.` When the atmospheric condition is such that the pointer 3T points to the left of 80% relative humidity (Fig. 1) the arm 04 and pin |05 engage and remain in constant contact by force of the weight H0 (or spring' 22, Fig. 6) thereby lighting the red lamp 66 by closure ofY the following circuit: current from one side of the source H5, wire |57, support |00, arm E04, pin |05, wire H9, lamp 05 and wire H0 to the other side of the current source.

As theY atmosphere becomes more loaded with moisture the element 95 lengthens by virtueV of the additional absorption., the resulting clockwise turning of the pointer1 shaft and pointer so that the pointer assumes the position mii, (Fig. l) will move the stud lill to `position |2| thereby lighting the white lamp 53 while thered lamp 06 remains lighted, thus indicatingv the beginning of the safe condition, the circuit then closed being as follows: current previously traced down to the arm |04 divides in its flow to the stud lill, arm |08, pointer shaft 25, bracket Sil, screw 98, wire H3, lamp (S3-and wire lit to the otherside of the current source. l

'I'he further addition of moisture both to the atmosphere and element 95 causes continued turning of the pointer to the position |22. The stud |01 then assumes the position i223. In doing so it moves the arm |04 away from pin 05; This breaks the circuit through the red lamp 05, but the circuit through the white lamp is continued, and remains unbroken as long asthe stud |07 keeps contact with arrn |051 The stud |07 thus comprises contactor means which controls the switch |014, |05, and when it touches the arm |04 it closes a circuit independent of the one controlled by the switch. The Whitev light Yindicates a safe operating condition.` Signalsy other than lamps may be used in lieu of lampsl 03, 00.

rI claim: v l v l. In a hygrometer operated switch, an absorptionfelement of spiral form, means `coupled-with said element for operation of the coupled element by lengthening and contraction of' the elcment, and an anchoragefor the free end-of said element, said anchoragecomprising a bracket, a yoke carried by the bracket having means to en-V gage the element, and, means to actuate the yoke in order to clamp down on the element. l

2. In a hygrometer operated switch, an open air chamber, and a closed switch compartment, a partition dividing the4 chamber from'the compartment, electrical switch apparatus located in the compartment, a shaft for actuating said apparatusextending fromthe compartment through the partition into the chamber, an absorption element located in the chamber and connected with the yshaft-for moving the shaft, said switch apparatus including an arm, a sleeve by which the arm is carried and means by which the sleeve is clamped on to the shaft, intertte'd bushings situated on opposite sides of the partition and providing a mount for the shaft, one of thebushings being overlapped by the sleeve, and gaskets to .make a gas tight seal, one of the gaskets being located in the overlap, the other gasket beingl 

